Code cleanup based on static analysis

Bug: 162188996
Test: gradlew test
Change-Id: Ie0a6334d0f970d9329e9fca581da68e6e5f32ac7
diff --git a/src/main/java/com/android/apksig/ApkVerifier.java b/src/main/java/com/android/apksig/ApkVerifier.java
index e323ed9..475ae42 100644
--- a/src/main/java/com/android/apksig/ApkVerifier.java
+++ b/src/main/java/com/android/apksig/ApkVerifier.java
@@ -1643,9 +1643,9 @@
 
             private SourceStampInfo(ApkSignerInfo result) {
                 mCertificates = result.certs;
-                mErrors = ApkVerificationErrorAdapter.getIssuesFromVerificationIssues(
+                mErrors = ApkVerificationIssueAdapter.getIssuesFromVerificationIssues(
                         result.getErrors());
-                mWarnings = ApkVerificationErrorAdapter.getIssuesFromVerificationIssues(
+                mWarnings = ApkVerificationIssueAdapter.getIssuesFromVerificationIssues(
                         result.getWarnings());
                 if (mErrors.isEmpty() && mWarnings.isEmpty()) {
                     mSourceStampVerificationStatus = SourceStampVerificationStatus.STAMP_VERIFIED;
@@ -2976,10 +2976,12 @@
     }
 
     /**
-     * Adapter for converting base ApkVerificationError instances to their IssueWithParams
-     * equivalent.
+     * Adapter for converting base {@link ApkVerificationIssue} instances to their {@link
+     * IssueWithParams} equivalent.
      */
-    public static class ApkVerificationErrorAdapter {
+    public static class ApkVerificationIssueAdapter {
+        private ApkVerificationIssueAdapter() {}
+
         private static final Map<Integer, Issue> sVerificationIssueIdToIssue = new HashMap<>();
 
         static {
@@ -3053,8 +3055,7 @@
 
         /**
          * Converts the provided {@code verificationIssues} to a {@code List} of corresponding
-         *
-         * @link IssueWithParams} instances.
+         * {@link IssueWithParams} instances.
          */
         public static List<IssueWithParams> getIssuesFromVerificationIssues(
                 List<? extends ApkVerificationIssue> verificationIssues) {
diff --git a/src/main/java/com/android/apksig/SourceStampVerifier.java b/src/main/java/com/android/apksig/SourceStampVerifier.java
index 0dad8e2..1f66464 100644
--- a/src/main/java/com/android/apksig/SourceStampVerifier.java
+++ b/src/main/java/com/android/apksig/SourceStampVerifier.java
@@ -81,7 +81,7 @@
     private SourceStampVerifier(
             File apkFile,
             DataSource apkDataSource,
-            Integer minSdkVersion,
+            int minSdkVersion,
             int maxSdkVersion) {
         mApkFile = apkFile;
         mApkDataSource = apkDataSource;
@@ -288,7 +288,7 @@
             ByteBuffer apkSignatureSchemeBlock,
             int apkSigSchemeVersion,
             Map<ContentDigestAlgorithm, byte[]> apkContentDigests,
-            Result result) throws NoSuchAlgorithmException {
+            Result result) {
         boolean isV2Block = apkSigSchemeVersion == VERSION_APK_SIGNATURE_SCHEME_V2;
         // Both the V2 and V3 signature blocks contain the following:
         // * length-prefixed sequence of length-prefixed signers
@@ -354,7 +354,7 @@
             CertificateFactory certFactory,
             Map<ContentDigestAlgorithm, byte[]> apkContentDigests,
             Result.SignerInfo signerInfo)
-            throws ApkFormatException, NoSuchAlgorithmException {
+            throws ApkFormatException {
         boolean isV2Signer = apkSigSchemeVersion == VERSION_APK_SIGNATURE_SCHEME_V2;
         // Both the V2 and V3 signer blocks contain the following:
         // * length-prefixed signed data
@@ -627,7 +627,7 @@
              * should be set to false to ensure only errors trigger a failure verifying the source
              * stamp.
              */
-            private final boolean mWarningsAsErrors = true;
+            private static final boolean mWarningsAsErrors = true;
 
             private SourceStampInfo(ApkSignerInfo result) {
                 mCertificates = result.certs;
diff --git a/src/main/java/com/android/apksig/apk/ApkUtils.java b/src/main/java/com/android/apksig/apk/ApkUtils.java
index 896ce3f..69399a7 100644
--- a/src/main/java/com/android/apksig/apk/ApkUtils.java
+++ b/src/main/java/com/android/apksig/apk/ApkUtils.java
@@ -25,13 +25,10 @@
 import com.android.apksig.internal.zip.ZipUtils;
 import com.android.apksig.util.DataSource;
 import com.android.apksig.zip.ZipFormatException;
-import com.android.apksig.zip.ZipSections;
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
-import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
@@ -99,11 +96,6 @@
         ZipUtils.setZipEocdCentralDirectoryOffset(eocd, offset);
     }
 
-    // See https://source.android.com/security/apksigning/v2.html
-    private static final long APK_SIG_BLOCK_MAGIC_HI = 0x3234206b636f6c42L;
-    private static final long APK_SIG_BLOCK_MAGIC_LO = 0x20676953204b5041L;
-    private static final int APK_SIG_BLOCK_MIN_SIZE = 32;
-
     /**
      * Returns the APK Signing Block of the provided APK.
      *
diff --git a/src/main/java/com/android/apksig/apk/ApkUtilsLite.java b/src/main/java/com/android/apksig/apk/ApkUtilsLite.java
index 992d6c6..13f2301 100644
--- a/src/main/java/com/android/apksig/apk/ApkUtilsLite.java
+++ b/src/main/java/com/android/apksig/apk/ApkUtilsLite.java
@@ -33,6 +33,8 @@
  * functionality.
  */
 public class ApkUtilsLite {
+    private ApkUtilsLite() {}
+
     /**
      * Finds the main ZIP sections of the provided APK.
      *
diff --git a/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtils.java b/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtils.java
index e92afdb..b91ccd8 100644
--- a/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtils.java
+++ b/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtils.java
@@ -52,7 +52,6 @@
 
 import java.io.IOException;
 import java.math.BigInteger;
-import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.security.DigestException;
@@ -85,7 +84,6 @@
 
 public class ApkSigningBlockUtils {
 
-    private static final char[] HEX_DIGITS = "0123456789abcdef".toCharArray();
     private static final long CONTENT_DIGESTED_CHUNK_MAX_SIZE_BYTES = 1024 * 1024;
     public static final int ANDROID_COMMON_PAGE_ALIGNMENT_BYTES = 4096;
     private static final byte[] APK_SIGNING_BLOCK_MAGIC =
@@ -241,69 +239,6 @@
         ApkSigningBlockUtilsLite.checkByteOrderLittleEndian(buffer);
     }
 
-    /**
-     * Returns new byte buffer whose content is a shared subsequence of this buffer's content
-     * between the specified start (inclusive) and end (exclusive) positions. As opposed to
-     * {@link ByteBuffer#slice()}, the returned buffer's byte order is the same as the source
-     * buffer's byte order.
-     */
-    private static ByteBuffer sliceFromTo(ByteBuffer source, int start, int end) {
-        if (start < 0) {
-            throw new IllegalArgumentException("start: " + start);
-        }
-        if (end < start) {
-            throw new IllegalArgumentException("end < start: " + end + " < " + start);
-        }
-        int capacity = source.capacity();
-        if (end > source.capacity()) {
-            throw new IllegalArgumentException("end > capacity: " + end + " > " + capacity);
-        }
-        int originalLimit = source.limit();
-        int originalPosition = source.position();
-        try {
-            source.position(0);
-            source.limit(end);
-            source.position(start);
-            ByteBuffer result = source.slice();
-            result.order(source.order());
-            return result;
-        } finally {
-            source.position(0);
-            source.limit(originalLimit);
-            source.position(originalPosition);
-        }
-    }
-
-    /**
-     * Relative <em>get</em> method for reading {@code size} number of bytes from the current
-     * position of this buffer.
-     *
-     * <p>This method reads the next {@code size} bytes at this buffer's current position,
-     * returning them as a {@code ByteBuffer} with start set to 0, limit and capacity set to
-     * {@code size}, byte order set to this buffer's byte order; and then increments the position by
-     * {@code size}.
-     */
-    private static ByteBuffer getByteBuffer(ByteBuffer source, int size) {
-        if (size < 0) {
-            throw new IllegalArgumentException("size: " + size);
-        }
-        int originalLimit = source.limit();
-        int position = source.position();
-        int limit = position + size;
-        if ((limit < position) || (limit > originalLimit)) {
-            throw new BufferUnderflowException();
-        }
-        source.limit(limit);
-        try {
-            ByteBuffer result = source.slice();
-            result.order(source.order());
-            source.position(limit);
-            return result;
-        } finally {
-            source.limit(originalLimit);
-        }
-    }
-
     public static ByteBuffer getLengthPrefixedSlice(ByteBuffer source) throws ApkFormatException {
         return ApkSigningBlockUtilsLite.getLengthPrefixedSlice(source);
     }
diff --git a/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtilsLite.java b/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtilsLite.java
index be14af8..40ae947 100644
--- a/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtilsLite.java
+++ b/src/main/java/com/android/apksig/internal/apk/ApkSigningBlockUtilsLite.java
@@ -38,6 +38,8 @@
  * utility functionality.
  */
 public class ApkSigningBlockUtilsLite {
+    private ApkSigningBlockUtilsLite() {}
+
     private static final char[] HEX_DIGITS = "0123456789abcdef".toCharArray();
     /**
      * Returns the APK Signature Scheme block contained in the provided APK file for the given ID
diff --git a/src/main/java/com/android/apksig/internal/apk/v1/V1SchemeVerifier.java b/src/main/java/com/android/apksig/internal/apk/v1/V1SchemeVerifier.java
index 2453f36..6d7e997 100644
--- a/src/main/java/com/android/apksig/internal/apk/v1/V1SchemeVerifier.java
+++ b/src/main/java/com/android/apksig/internal/apk/v1/V1SchemeVerifier.java
@@ -53,7 +53,6 @@
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
-import java.nio.ByteOrder;
 import java.security.InvalidKeyException;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
diff --git a/src/main/java/com/android/apksig/internal/zip/ZipUtils.java b/src/main/java/com/android/apksig/internal/zip/ZipUtils.java
index c6f074d..9d9da15 100644
--- a/src/main/java/com/android/apksig/internal/zip/ZipUtils.java
+++ b/src/main/java/com/android/apksig/internal/zip/ZipUtils.java
@@ -17,7 +17,6 @@
 package com.android.apksig.internal.zip;
 
 import com.android.apksig.apk.ApkFormatException;
-import com.android.apksig.apk.ApkUtilsLite;
 import com.android.apksig.internal.util.Pair;
 import com.android.apksig.util.DataSource;
 import com.android.apksig.zip.ZipFormatException;
diff --git a/src/test/java/com/android/apksig/SourceStampVerifierTest.java b/src/test/java/com/android/apksig/SourceStampVerifierTest.java
index 0ff5a81..2235657 100644
--- a/src/test/java/com/android/apksig/SourceStampVerifierTest.java
+++ b/src/test/java/com/android/apksig/SourceStampVerifierTest.java
@@ -16,38 +16,16 @@
 
 package com.android.apksig;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
-import static org.junit.Assume.assumeNoException;
 
-import com.android.apksig.apk.ApkFormatException;
-import com.android.apksig.internal.util.AndroidSdkVersion;
-import com.android.apksig.internal.util.HexEncoding;
 import com.android.apksig.internal.util.Resources;
 import com.android.apksig.util.DataSources;
 
-import org.junit.Assume;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-import java.io.IOException;
 import java.nio.ByteBuffer;
-import java.security.InvalidKeyException;
-import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
-import java.security.PublicKey;
-import java.security.Security;
-import java.security.Signature;
-import java.security.cert.CertificateFactory;
-import java.security.cert.X509Certificate;
-import java.util.Collection;
-import java.util.List;
-import java.util.Locale;
-import java.util.Objects;
-import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 @RunWith(JUnit4.class)
 public class SourceStampVerifierTest {
@@ -222,7 +200,7 @@
         return builder.build().verifySourceStamp(expectedCertDigest);
     }
 
-    private void assertVerified(SourceStampVerifier.Result result) {
+    private static void assertVerified(SourceStampVerifier.Result result) {
         if (result.isVerified()) {
             return;
         }